A radio access scheme and a radio network (hereinafter, referred to as “Long Term Evolution: LTE” or “Evolved Universal Terrestrial Radio Access: EUTRA”) of cellular mobile communication have been discussed in 3rd Generation Partnership Project (3GPP). In LTE, a base station apparatus is also referred to as an eNodeB (evolved NodeB), and a terminal device is referred to as user equipment (UE). LTE is a cellular communication system in which a plurality of areas covered by the base station device is arranged so as to have a cell shape. A single base station apparatus may manage a plurality of cells.
LTE corresponds to time division duplex (TDD). LTE employing the TDD scheme is also referred to as TD-LTE or LTE TDD. In TDD, an uplink signal and a downlink signal are subjected to time division multiplexing.
In 3GPP, it is discussed that a traffic adaptation technology and an interference reduction technology (DL-UL Interference Management and Traffic Adaptation) is applied to TD-LTE. The traffic adaptation technology is a technology in which a ratio of uplink resources and downlink resources is changed depending on traffic of an uplink and traffic of a downlink. The traffic adaptation technology is also referred to as dynamic TDD.
In NPL 1, a method of using a flexible subframe is proposed as a method of realizing traffic adaptation. A base station apparatus can receive an uplink signal or transmit a downlink signal in a flexible subframe. In NPL 1, a terminal device considers the flexible subframe as a downlink subframe, as long as the base station apparatus does not perform an instruction of transmitting the uplink signal in the flexible subframe.
NPL 1 discloses that hybrid automatic repeat request (HARQ) timing for a physical downlink shared channel (PDSCH) is determined based on an UL-DL configuration (uplink-downlink configuration) which is newly applied, and a HARQ timing for a physical uplink shared channel (PUSCH) is determined based on the first UL-DL configuration.
NPL 2 discloses that (a) UL/DL Reference Configuration is applied, and that (b) a certain subframe may be scheduled for either of an uplink or a downlink, by dynamic grant/assignment from a scheduler.